A fetus growing inside the mother's womb does not use its lungs to breathe until birth, so its circulatory system is different from that of a newborn baby. Instead of the lungs supplying the oxygen-rich blood the fetus needs, the fetal heart has an opening between the upper chambers (the right and left atria) called the foramen ovale.

The foramen ovale lets blood flow directly from the right atrium to the left atrium during fetal development. The foramen ovale is an important part of the fetal circulatory system before birth, but it is supposed to close soon after birth. In most cases, when babies are born and start to use their lungs to breathe, it causes pressure in the left side of the heart. This pressure forces the foramen ovale closed.

What is patent foramen ovale?

The word "patent" means unobstructed, or open. So, patent foramen ovale (PFO) means that the foramen ovale stays open after birth. About 1 out of every 3 or 4 people has PFO. There are no risk factors for PFO, but we do know that when babies are born with congenital heart disease, it is common for their foramen ovale to stay open.

What are the signs and symptoms?

Most people with PFO go their whole lives without any symptoms. In fact, PFO is usually discovered only when patients undergo tests for other heart conditions. In some cases, babies with PFO may have a bluish tint to their skin (called cyanosis) when they are crying or straining during a bowel movement, but this is a very rare sign. If babies with PFO have cyanosis, it is usually because they have other heart defects, as well.

What are the risks?

Unless there are other heart defects, PFO usually does not cause any problems. However, some studies have shown that if you have a PFO, you may have an increased risk of

Stroke. Doctors think this is because older people are more likely to develop blood clots in the veins in their legs. These clots could travel in the bloodstream from the legs to the heart. If a person has a PFO, a clot could pass through the opening, from the right side of their heart to the left. From there, the clot may travel to the brain, where it could block an artery and cause a stroke.

A stroke may also be more likely in people with PFOs if they also have an atrial septal aneurysm. This is a congenital heart defect that causes the wall between the left and right atria to bulge. (This wall is called the septum.) If the septum bulges into either of the atria, it might cause blood clots that could travel in the bloodstream to the brain.

Heart attack. Older people with PFOs may have an increased risk of heart attack for the same reason they may have an increased risk of stroke. Blood clots from the legs may travel to the heart and into one of the coronary arteries. If the clot becomes stuck in the coronary artery, the blockage will shut off all blood flow to the section of heart muscle fed by the artery.

Migraine with aura. Migraines are very painful headaches. In people who have migraines with aura, these headaches cause blurry vision and blind spots. Some studies have linked PFOs with migraines and some PFO patients have found that their migraine headaches go away after the PFO is closed.

How is PFO diagnosed?

Most times, a PFO is found during tests for other heart problems. If your doctor thinks you might have a PFO, he or she may order the following tests:

Echocardiography to see the structure of your heart and how it is working. Color Doppler echocardiography is especially good for seeing the blood flow between the left atrium and the right atrium.

Saline contrast study (or bubble study) to watch how blood flows through your heart. In this test, a salt solution is shaken until bubbles form. The harmless solution is then injected with a needle into a vein in your arm. The bubbles will travel to the right side of your heart. Doctors then use echocardiography to see where the bubbles go from there. If the bubbles travel to the lungs, then there is no PFO. If the bubbles travel to the left side of your heart, then there is probably a PFO.

Transesophageal echocardiography to see a more detailed picture of how blood flows through your heart. This test may be used in combination with color Doppler or a bubble study.

How is PFO treated?

Most people with PFO do not need treatment. Patients who do need treatment may take medicines or have a percutaneous coronary intervention to close the PFO. In more serious cases, surgery may be needed.

Transcatheter interventionsA transcatheter intervention is the most common way to close a PFO. This procedure is done in the cardiac catheterization laboratory to insert a closure device, plugging the hole.

SurgerySometimes surgery is done to close a PFO. Usually, doctors only recommend surgery if patients are already having heart surgery for another reason. For example, a child may need surgery to correct other congenital heart defects, so the surgeon may go ahead and close the PFO at the same time. Surgery requires opening the heart and stitching the PFO closed. In some cases, this can be done using limited-access techniques.